Vapor-rectifier and method of manufacture.



J. LE n. HAYDEN, VAPOR RECTIFIER AND METHOD OF MANUFACTURE.

APPLICATION FILED 23.10, 1907- ;BEHEWED APR. 13, 19M.

, 1,041,076. Patented Oct. 15. 1912.

Witnesses: lnven cor WW Joseph LeRy Hayden,

Atty.

UNITED STACES PATENT orrron JOSEPH L. R. HAYDEN, OF' SCHENEGTADY. NEW YORK, ASSIGNOR 'IO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

VAPOR-RECTIFIER AND METHOD OF MANUFACTURE.

Specification of Letters Patent.

Patented Oct. 15,1912.

Application filed April 16, 1907, Serial No. 368,489. Renewed April 13, 1912. Serial No. 690,657.

' DEN, a citizen of the UnitedStates, residing at Schenectad county of Schenectady, State of New ork, haveinvented certain new and useful Improvements in Vapor- Rectifiers and Methods of-Manufacture, of which the following is a specification.

Vapor rectifiers are well adapted for use on highvoltage systems, and such rectifiers of the mercury arc type have been successfully operated in constant current systems wherethe voltage of the alternating current supply is several thousand volts.

In order that vapor rectifiers may operate to the best advantage on high voltage current, the vacuum of the rectifier must be very good and must be maintained high during normal life of the tube. A good vacuum can be produced in the device before it is sealed off fromthe-pump, but unfortunately this vacuum is subject to change by gases given ofi within the tube. .It sometimes happens that mercury occurs near the anodes, either from condensation or other cause, and that this mercury causes arcing or striking back when the tube is started on a heavy load. Such arcing may liberate gas from the anodes and thus slightly impair the vacuum.

It is the object of this invention to provide means for the elimination of whatever gas may exist in the tube after it is sealed oif, or to take up any gas that may be produced in the tubeeduring its operation.

According to my invention, a quantity of finely divided graphite or carbon or other material of high gas absorbing quality as platinum or palladium is arranged in the tube in such a way that it will absorb any traces of gas, even from a very high vacuum. The desired result may be attained in various ways as hereinafter set forth.

In general, the rectifier tube, or at least a portion of the same, is covered with a coating of graphite or carbon produced by disintegration of a heated carbon or graph- Figure 1 illustrates a mercury vapor reotifier suitable foruse in high voltage systems; and Fig. 2 iltustrates'a similar tube provided with a carbon filament in the condensing chamber.

The rectifier tube shown in Fig. 1 comprises a single condensing chamber 1, a mercury cathode 2, arranged immediately below the condensing chamber, main anodes 3 and 4 located in bent tubes arranged at an angle to the condensing chamber, and auxiliary mercury anodes 5 and 6 for starting purposes. Tubes embodying these features are well known to persons skilled in the art.

Electrodes 3 and 4 may be of raphite and may be connecteddirectly to t e source of high voltage supply. If a proper vacuum is maintained within the tube, the anodes 3 and 4 will not are across from one to another, but will deliver current only to tlfe mercury cathode 2. It sometimes happens, however, that mercury condenses back of one of the anodes and develops an unstable condition by virtue of which an arc may form to the carbon as cathode. This foreign mercury may be produced by sudden chilling of the tube when the circuit is opened, or by various other causes.

When the are forms to the graphite electrode as cathode, a considerable quantity of gas is given off and the reliability of the tube is greatly reduced. To absorb this gas I provide certain portions of the tube with a very thin coating of carbon or graphite put on in such a way that itv adheres tightly to the glass and has a high absorbing power for gases. The coating may be applied to various parts of the tube, but I prefer to apply it either to the anode arms or to the condensing chamber or both. When the coating is to be applied to the condensing capable of maintaining a'very high voltage" alternating or oscillating arc to the auxiliary anode 7 as cathode. A high frequency Tesla transformer giving a 6 or 8 inch spark at several hundred thousand cycles may be used. This high potential arc serves to disintegrate the solid electrode 7 to produce vapor which condenses on the walls of the envelop. .I find that during this treatment large quantities of gas are given off by the electrode under treatment, and avigorous pumping must be maintained. This is the case even though the electrode may havepreviously been treated at high current in a vacuum to remove occluded gases as completely as possible.

As av result of the above procedure, the top of the condensing chamber becomes cov- .ered with a thin adherent coating of gas-free graphite or carbon.

In. case it is desired to similarly treat the anode arms, the high potential arc is established between "the mercury cathode and either anode, or from one anode to another. By keeping up a vigorous pumping during the disintegration of the carbon electrodes, the coatings on the walls of the tube are sure to have a high gas absorbing power. It will, of course, be understood that this high voltage treating current has "avoltage I greatly in excess of the normal operating Voltage of the rectifier, even though the latter be of that type commonly known as a high voltage rectifier.

As an alternative method of coating the tube with carbon I may disintegrate a carbonaceous filament, either by sending current through it or by using it as an electrode for an arc. Referring to the drawing, Fig. 2 illustrates a rectifier tube provided with a graphitized base filament 8 provided with leading-in conductors 9 and 10. Before disintegration of the filament, the tube must be pumped out and the anodes must be treated with current to remove the occluded gas as completely as possible. Current is then sent through the filament to heat it up gradually until it finally breaks through and produces an arc between the broken ends. This arc continues the disintegration of the filament with the production of a coating of gas-free carbon or graphite on the interior of the condensing chamber. If the surface to be covered with carbon is not too large, the filament can be disintegrated by using it as anode for an arc, though in' this case the disintegration probably takes place'because of the .heat alone and not because of the cathode effect. I have mentioned carbon as suitable material for producing this gas absorbent coating on the interior of the envelop, but I may also mention platinum and palladium as having a gas absorbing power suitable for this purpose.

The carbon deposited, as above described,

covers the; glass with a coating which, when thin, is yellowish brown and transparent and then becomes opaque and black. It is of metallic appearance and adheres to the glass so well that the impact of mercury does not appreciably loosenit. As the; disintegrated carbon oflers an enormous surface for the absorption of gas, the total Weight 'of disintegrated carbon may be very small, and may constitute only a small part of the graphite electrode or filament.

When the main anodes are disintegrated by means of a high voltage alternating current, after the rectifier has been exhausted, or before it is taken off the pump, the 'film is deposited on the glass walls in the immediate neighborhood of the anodes and because of its porous nature and low thermal conductivity protects the anodes from rapid cooling when the rectifier is shut down. This reduces the liabi ity of condensed mercury at or near the anodes.

What I claim as new and desire to secure by Letters Patent of the United States, is, 1. A mercury-vapor device comprising a vaporizable cathode, one or more'anodes and a highly exhausted envelop with a thin gas-absorbing coating of carbonaceous material.

2. A vapor rectifier having anodes, a vaporizable cathode, and an evacuated envelop with a thin coating of gas-absorbing material to limit the quantity of gas between said anodes.

3. The combination of an evacuated envelop, electrodes therein, at least one of which is of vaporizable metal, and a carbonaceous coating for said envelop adjacent to at least one of said electrodes.

4. The combination of an evacuated envelop, anodes and a vaporizable cathode therein, and means for depositing disintegrated carbonaceous material in a thin layer on a portion of said envelop.

5. The method which consists in pumping out the envelop of a vapor electric device and then coating at least a part of the inner wall of said envelop with a gas-absorbing medium while the pumping operation is continued.

6. The method of exhausting a high voltage rectifier having an envelop and electrodes one at least of which is vaporizable, which consists in pumping out the envelop to a high-vacuum and then disintegrating a carbonaceous body Within said envelop and producing a thin gas-absorbing coating of carbonaceous material on said envelop While ,the pumping operation is continued.

7. The method of coating an envelop with a gas-absorbing material, which consists in disintegrating a solid body of said material by a high-voltage electrical discharge thereto, and simultaneously maintaining a highvacuum in said envelop.

8;. The process which consists in coating an evacuated envelop with gas-absorbing material, by disintegrating a solid body therein operating as a cathode for an electrical discharge during the operation of exhaustion. J a f 9. The process which consists in evacuating a rectifier tube containing main anodes and a cathode, then disintegrating with electrical energy a carbonaceous body located therein, and maintaining a high degree of evacuation during, disintegration of said body.

10. A vapor rectifier having an evacuated envelop with a condensing chamber, and a thin coating of gas-absorbing material within said condensing chamber.

11. A vapor rectifier having arms carrying anodes, said arms being coated near the anodes with a thin layer of gas-absorbing material.

12. In a vapor electric device, the combination of an anode arm having an anode near the end'thereof, and a thin carbonaceous coating within said anode arm and surrounding said anode.

13. A mercury vapor device comprising a vaporizable cathode, one or more anodes and a highly exhausted envelop with a thin gasabsorbing coating of finely divided material.

14. The method which consists in pumping out an envelop to a high vacuum and then disintegrating a solid body therein operating as an electrode for an electrical discharge, thereby depositing a film of finely divided material on said envelop.

15. The process which consists in pumping out an envelop to a high vacuum and then disintegrating a solid body by high frequency electrical discharge while the pumping operation is continued.

In witness whereof, I have hereunto set my hand this 13th day "of April, 1907.

JOSEPH L. R. HAYDEN.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

